If you look on the
Archived site, it says that Visage was the program they recommended to install boot panels, which can be found
here.
However, I think I don't think the mods work on recent Macs like they did back then - you can change the login screen, and
BootXChanger to change the boot logo, but not quite to the same extent as before.
Unless, of course, you have a PPC Mac running 10.3 or earlier.